This relates generally to electronic devices, and more particularly, to electronic devices with displays.
Electronic devices often include displays. For example, cellular telephones, tablet computers, and laptop computers often include displays for presenting information to a user.
Liquid crystal displays contain a layer of liquid crystal material sandwiched between upper and lower polarizers. Pixels in a liquid crystal display contain thin-film transistors and electrodes for applying electric fields to the liquid crystal material. The strength of the electric field in a pixel controls the polarization state of the liquid crystal material and thereby adjusts the brightness of the pixel. A liquid crystal display may have an array of color filter elements to provide the display with the ability to display color images.
The pixels in the liquid crystal display can be illuminated using a backlight unit. The backlight unit may include a light guide layer. The light guide layer may be formed from a transparent material such as a transparent polymer. An array of light-emitting diodes may emit light into the edge of the light guide layer. The light that is emitted into the edge of the light guide layer may be distributed throughout the light guide layer in accordance with the principle of total internal reflection.
The light guide layer may be provided with light scattering features that scatter the light that is traveling within the interior of the light guide layer. Light that is scattered outwards from the light guide layer through the pixels of the liquid crystal display can serve as backlight for the display.
Display brightness can be adversely affected by the optical characteristics of the display. As an example, the lower polarizer in a display may transmit only a fraction of the light that scattered outwards from the light guide layer, decreasing backlight efficiency and the brightness level of the display.
It would therefore be desirable to be able to provide improved displays such as improved backlit liquid crystal displays.